Screen broken by water damage iPhone 6s plus

So i dropped my phone to water ( in a sink of water ) as soon as i got it out of water immediately. At first , i thought it was fine because the phone just dipped into water only almost 3,4s . After that, i played few games and few minutes later the touching function doesn't work then i turned off and covered it by rice for few hour. Then i turn it on and the screen works again. but lately, there was some problem with my screen , sometime it doesn't work(70%), sometime it works (30%). So what should i do know ?

Many Thanks .